Exercise

What conclusion can you draw from the following observations on a resistor made of alloy manganin?

A low voltage supply from which one needs high currents must have very low internal resistance. Why?

A heating element using Nichrome connected to a $230 \mathrm{V}$ supply draws an initial current of $3.2 \mathrm{A}$ which settles after a few seconds to a steady state value of $2.8 \mathrm{A}$. What is the steady state of heating element if the room temperature is $27 °\mathrm{C}$? Temperature coefficient of resistance of Nichrome averaged over temperature range involved is $1.70\times {10}^{-4} {\mathrm{C}}^{-1}$.

Ohm's law does not apply to which of the following?

Is Ohm’s law universally applicable for all conducting elements? If not, give examples of elements which do not obey Ohm’s law.

In current electricity, Ohm's law is obeyed by all _____.

In the given figure, the value of $I$ will be

A secondary cell after long use has an emf of $1.9 \mathrm{V}$ and a large internal resistance of $380 \mathrm{\Omega }$. What maximum current can be drawn from the cell? Could the cell drive the starting motor of a car?